Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions that damage the cells. Antioxidants terminate these chain reactions by removing free radical intermediates and inhibit other oxidation reactions.
An antioxidant is a molecule capable of slowing or preventing the oxidation of other molecules. There are different attributes to classify the antioxidants. The first attribute is based on the function (primary and secondary antioxidants). The second attribute is based on enzymatic and non-enzymatic antioxidants:
Primary antioxidants
They are the chain breaking antioxidants which react with lipid radicals and convert them into more stable products. Primary or natural antioxidants can be extracted from plants, microorganisms and animal tissues. Antioxidants of this group are mainly phenolics, in structure and include the following: Antioxidant minerals, antioxidant vitamins and phytochemicals which include flavonoides, catechins, carotenoids, β-carotene, lycopene, diterpene of, black pepper, thyme, garlic, cumin and their derivatives.
Antioxidants minerals are co factor of antioxidants enzymes. Their absence will definitely affect metabolism of many macromolecules such as carbohydrates. Examples include selenium, copper, iron, zinc and manganese.
Antioxidants vitamin is needed for most body metabolic functions. They include-vitamin C, vitamin E, vitamin B.
Secondary antioxidants
These are phenolic compounds that perform the function of capturing free radicals and stopping the chain reactions. They react with hydroperoxides to yield non-radical, non-reactive products. They are compounds produced artificially and added to processed or pre -packaged food to prevent rancidity, browning.
Secondary antioxidants can retard lipid oxidation through a variety of mechanisms, including chelating of transition metal ions, oxygen scavenging, replenishing hydrogen to primary antioxidants, absorbing UV radiation and deactivation of reactive species.
The compounds include: Butylated hydroxy anisole (BHA), butylated hydroxy toluene (BHT) and propyl gallate (PG).
Classification of antioxidants
